The present invention relates generally to high-speed data communication systems, and specifically to Digital Subscriber Line systems.
Digital Subscriber Line (DSL) is a modem technology that enables broadband digital data to be transmitted over twisted-pair wire, which is the type of infrastructure that links most home and small business subscribers to their telephone service providers. DSL modems enable users to access digital networks at speeds tens to hundreds of times faster than current analog modems and basic ISDN service. DSL thus opens the most critical bottleneck in local-loop access to high-speed networks, such as Asynchronous Transfer Mode (ATM) and Internet Protocol (IP) networks, without requiring major investments in new infrastructure. A range of DSL standards have been defined, known generically as xe2x80x9cxDSL,xe2x80x9d wherein the various standards have different data rates and other associated features but share common principles of operation.
DSL subscribers are connected to high-speed networks through Digital Subscriber Line Access Multiplexer (DSLAM) systems. Because of the high cost of network bandwidth, a single DSLAM must typically be designed to serve between 100 and 1000 subscribers and to concentrate their traffic through one or a few high-speed network trunks. The need to serve such a large and potentially variable number of subscribers in the one DSLAM has led to the development of xe2x80x9cmulti-shelfxe2x80x9d access architectures. In the physical implementation of such systems, each of the shelves holds a switching unit and a group of line cards. Each line card has a number of ports that serve network subscribers. Each switching unit links the shelf to the network trunk (either directly or through the switching unit of another shelf) and multiplexes the network connection among the line cards.
In order to reduce maintenance costs, DSLAM systems are typically configured so that, insofar as possible, management and maintenance activities are carried out using a remote management station. Optimally, the management station communicates xe2x80x9cin-bandxe2x80x9d with the switching units, i.e., via the high-speed network. Alternatively, the management station may communicate with the master unit via an xe2x80x9cout-of-bandxe2x80x9d network, such as an Ethernet network, or by a point-to-point (PPP) dial-up connection. The object of this configuration is to minimize the number of service calls that a maintenance engineer or technician must make to the site of the DSLAM.
It is also desirable that the system be designed so that, when a service call turns out to be unavoidable, it can be made by a technician of minimal skill, whose role is limited, for example, to replacement of a card that has been identified as faulty. Each of the switching units typically has its own, unique configuration settings, however. Therefore, when one of the switching units needs to be replaced, the service person must generally program in the configuration of the new unit before it can become operational. The remote management station can only begin to communicate with the new switching unit after the proper configuration has been programmed.
It is an object of the present invention to provide a network access system that automatically configures itself upon start-up or replacement of components.
It is a further object of some aspects of the present invention to enable a connection to be made automatically, preferably an in-band connection, between the network access system and a management station upon start-up of the system or replacement of components.
It is still a further object of some aspects of the present invention to reduce the need for service personnel on the site of the network access system to reprogram configuration settings of the system after a failure or component replacement.
In preferred embodiments of the present invention, a network access multiplexing system comprises one or more shelves, each shelf comprising a switching unit, linked to the network, and one or more line cards, having ports that serve respective network subscribers. Preferably, the shelves comprise a master shelf, having a master switching unit connected to the network, and a plurality of slave shelves, having slave switching units linked to the network through the master switching unit. For each shelf, the respective switching unit comprises a non-volatile memory, which stores operating configuration parameters for the shelf. At least one of the line cards, and preferably all of the line cards, also comprise memory, most preferably random-access memory (RAM).
The configuration parameters set in the non-volatile memory of the switching unit are backed up in the RAM of the line cards. If it becomes necessary to replace the switching unit, the new switching unit automatically copies the backup configuration parameters from the RAM of the line cards and stores them in its own non-volatile memory. Thus, the configuration of the shelf is maintained, generally without the need for service personnel to enter new configuration settings, and the new switching unit is immediately accessible for remote, in-band access by a management station.
There is therefore provided, in accordance with a preferred embodiment of the present invention, multiplexing apparatus for providing access to a high-speed network over a plurality of subscriber lines, including:
one or more line cards including ports to the subscriber lines, at least one of the line cards including a volatile memory for storing backup configuration parameters of the apparatus; and
a switching unit, including:
a non-volatile memory, adapted to store operating configuration parameters;
a controller, operative to receive the backup configuration parameters stored in the volatile memory and to update the operating configuration parameters in the non-volatile memory responsive to the backup configuration parameters; and
a communication interface, over which the switching unit is coupled to communicate with the network in accordance with the operating configuration parameters so as to link the ports of the line cards to the network.
Typically, the ports include Digital Subscriber Line ports.
In a preferred embodiment, the apparatus includes a multi-shelf access system, wherein the one or more line cards and the switching unit together occupy one of the shelves. Preferably, the switching unit includes a master switching unit, which is further coupled to link one or more slave switching units, located on other ones of the shelves, to the network. Most preferably, the operating configuration parameters define an interface configuration between the master switching unit and the one or more slave switching units.
Additionally or alternatively, the switching unit includes a slave switching unit, and the communication interface is coupled to communicate with the network via a master switching unit on another one of the shelves. Preferably, the operating configuration parameters define an interface configuration between the slave switching unit and the master switching unit.
Preferably, the controller is operative to receive the backup configuration parameters and to update the operating configuration parameters upon a start-up of the switching unit. Further preferably, the controller is operative upon the start-up to store the backup configuration parameters in the non-volatile memory in place of the operating configuration parameters previously stored therein. Most preferably, responsive to the backup configuration parameters stored in the non-volatile memory in place of the operating configuration parameters, the switching unit is operative to communicate over the network with a management station following installation of the unit substantially without setting of the parameters by a human operator. Additionally or alternatively, following the start-up, the controller is operative to write the operating configuration parameters to the line cards for storage in the volatile memory.
There is also provided, in accordance with a preferred embodiment of the present invention, a method for providing access to a high-speed network, including:
coupling a switching unit to interface with the network in accordance with operating configuration parameters stored in the switching unit;
linking one or more line cards to communicate with the network through the switching unit, each line card including one or more ports to respective subscriber lines;
storing backup configuration parameters in at least one of the line cards; and
upon a start-up of the switching unit, receiving the backup configuration parameters from the at least one of the line cards and, responsive to the received backup parameters, updating the operating configuration parameters.
Preferably, the method further includes:
installing the switching unit in a system already including the at least one of the line cards in which the backup configuration parameters are stored; and
responsive to updating the operating configuration parameters after installing the switching unit, establishing communications over the network between the switching unit and a management station substantially without setting of the parameters by a human operator.